Scissor-Wings for NASA

Odd design cuts the cost of high-speed flying

Rolling down the runway, the little twin-engine jet looked like any rich man's weekend toy, but as it picked up speed over the California airstrip and began climbing, the craft underwent a bizarre and visually unsettling transformation. Its wing began slowly to swing around--its right half angling forward in the direction of flight, the left back.

This flying pair of scissors looked like the joke of some eccentric inventor. In fact, the 38-ft.-long aircraft is a test design that comes from the same no-nonsense people who created the space shuttle. Pursuing what NASA officials refer to as the "small A" (for the less publicized, low-budget aeronautics in their agency's name), they built the single-seat model to overcome two major obstacles in supersonic flight: high fuel consumption and thundering noise.

At high speeds, an aircraft operates most efficiently if its wings intercept the air at an angle. Trouble occurs when the plane is flying at slower, subsonic speeds: swept-back wings reduce lift and increase fuel consumption. One way designers have tried to overcome this problem is by creating "variable geometry" aircraft that can swing back their wings at higher speeds and bring them forward for reduced speeds, especially during takeoffs and landings, when the plane needs maximum lift.

But swing-wing planes are difficult to build. They require greater structural strength, weigh more and burn more fuel than a comparable fixed-wing aircraft. As far back as 1945, Robert T. Jones of NASA's Ames Research Center, who proposed the first U.S. swept-wing aircraft, saw a simple solution: a single, rigid wing that would swing on a single pivot point. The oblique wing, as he called it, would vastly simplify the structural problem. The fact that one end of the wing would be pointing forward might look odd, but it was, he realized, aerodynamically unimportant. In high-speed flight, what matters is the angle at which the wing meets the onrushing air.

Jones, a largely self-taught aeronautical genius who never finished college, did not pursue his idea until the late 1960s. ("I didn't push it very much because it looked pretty weird.") By then, the U.S. was seriously considering construction of a large SST, a commercial supersonic transport, and wind-tunnel tests confirmed that the oblique wing should do the things he claimed it could. As Jones explains, at supersonic speeds conventional swept-back wings create noticeable pressure on each other, like two motorboats speeding side by side through the water and slamming waves into each other's hulls. But this mutual interference is reduced when one boat pulls ahead of the other. Despite raised eyebrows at the plane's odd appearance and fears that the forward wing might break off at high speed, NASA finally built a test version (at a bargain basement tab of $218,000), and has found it performs up to expectations.

Jones' oblique wing is heading into an uncertain future, nevertheless. A full-scale plane big enough to carry 150 passengers should be twice as fuel efficient as the 100-passenger Concorde. But its maximum speed of 1 1/2 times the speed of sound (Mach 1.5) would be 25% less than the Anglo-French craft's Mach 2.04. A likelier role for a scissor plane might be as a military patrol craft whose pivoting wing would allow both long flights and the bursts of speed needed for hot pursuit. NASA thinks the flying scissors also has a role as a cost-cutting corporate jet.

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